XP CHANGING COMP PWORDS

Hey guys.
Can anyone help me with changing passwords on xp ?
I want to change a password of a computer that i don't already know, my friend recently got on and changed it so that i can't even log on.
Anyone know how to change it? Thanks.

when you turn on the computer spam the F8 button until a safe mode window opens then select run windows in safe mode with networking.
from here follow these steps
1.logon the admin
2.goto control panel
3.select user accounts
4.select the account
5.delete the password
6.restart your comp and logon to the account u deleted the pass on
7.create your new password

or go to cmd (if its not blocked)
then go
1. net user (name) (pass)
2. hit enter